Sharif Digital Repository

Dynamic contact angle measurement; as a standard method for surface wettability analysis, is usually conducted through the analysis of sessile drops formed following the low rate injection of fluid from beneath through a drilled hole via an injection needle. However, understanding/characterizing the changes of drop contact angle from the point where the flat solid surface begins is not well discussed yet. Moreover, during the evaluation of size-dependent behavior of contact angle of millimeter-scale drops, the effect of the drilled hole is ignored. In this regard, in the current study, the experimental and thermodynamic characterizations of the sessile drop advancing contact angle... 

Water flooding is widely applied for pressure maintenance or increasing the oil recovery of reservoirs. The heterogeneity and wettability of formation rocks strongly affect the oil recovery efficiency in carbonate reservoirs. During seawater injection in carbonate formations, the interactions between potential seawater ions and the carbonate rock at a high temperature can alter the wettability to a more water-wet condition. This paper studies the wettability of one of the Iranian carbonate reservoirs which has been under Persian Gulf seawater injection for more than 10 years. The wettability of the rock is determined by indirect contact angle measurement using Rise in Core technique.... 

In this report, sessile drop technique was employed to study the wetting of alumina by pure aluminium. Contact angle of pure aluminium on the surface of polycrystalline alumina substrate was studied in the temperature range of 750-1100 °C. Electron microscopy and EDX analysis were employed to examine the possible reactions at the melt-substrate interface. It was found that at temperatures in excess of 1050 °C molten aluminium can wet alumina. No reaction layer was detected at the Al/Al2O3 interface. © 2007 Elsevier B.V. All rights reserved  

In this paper, the elastic contact problem of an asymmetrical shallow wedge with a half-plane is considered. The potential function of the contact problem has been obtained through a simple approach. This approach simplifies the routine method of determination of potential functions in elastic contact problems. Then this approach was utilized to solve the aforementioned geometry under frictionless and frictional condition. Utilization of the new relation not only simplifies the procedure of solving contact problems but also is very helpful for fretting fatigue studies. © 2007 Elsevier Ltd. All rights reserved  

Recently, super gas wet and gas wet surfaces have been extensively attended in petroleum industry, as supported by the increasing number of publications in the last decade related to wettability alteration in gas condensate reservoirs. In many cases, contact angle measurement has been employed to assess the wettability alteration. Even though contact angle measurement seems to be a straightforward approach, there exist many misuses of this technique and consequently misinterpretation of the corresponding results. In this regard, a critical inspection of the most recent updated concepts and the intervening parameters in the contact angle based wettability evaluation of liquid-solid-gas... 

This paper deals with the dynamics of rising bubbles attached to a vertical wall under different wettability conditions. Even though, bubbles rising freely in a liquid have extensively been studied, bubbles attached to a wall have not been fully understood. Therefore, in this work, rising bubbles attached to a vertical wall were numerically investigated by applying the ALE method along with adaptive mesh refinement schemes to properly resolve the bubble interface and its deformation. To consider wall wettability effects, different contact angles of 45° 90° and 105° were considered along with the case of freely rising bubbles. The problem was carried out at different Bond numbers of 0.27,... 

In this study, four types of mixed matrix membranes were fabricated using polysulfone (as the base polymer) and different contents of graphene oxide (GO) nanosheets (as modifier) through wet phase inversion method. Based on the amounts of GO (0, 0.5, 1, and 2 wt%), the synthesized membranes named as M1, M2, M3, and M4, respectively. The membranes characteristics were evaluated using FE-SEM, FT-IR, and water contact angle measurements. In addition, the performance of the prepared membranes was investigated in terms of basic parameters: filtrate water flux, nitrate removal efficiency, and antifouling properties. Results showed significant improvements of the characteristics of modified... 

In this study, the range of applicability for Cassie–Baxter and Wenzel equations for estimating apparent contact angle on rough surfaces is numerically discussed. To do this, circular drops with different sizes are simulated on rough surfaces with a square pillar pattern and randomly distributed cylindrical pillar. With the aid of numerical method, the local surface fraction, local length fraction and local roughness factor for drops with different sizes on the surface are computed. Then, the global surface fraction and global roughness factor have been compared with the local surface fraction and local roughness factor, respectively. Local surface and local length fractions, as well as... 

In this study, four types of mixed matrix membranes were fabricated using polysulfone (as the base polymer) and different contents of graphene oxide (GO) nanosheets (as modifier) through wet phase inversion method. Based on the amounts of GO (0, 0.5, 1, and 2 wt%), the synthesized membranes named as M1, M2, M3, and M4, respectively. The membranes characteristics were evaluated using FE-SEM, FT-IR, and water contact angle measurements. In addition, the performance of the prepared membranes was investigated in terms of basic parameters: filtrate water flux, nitrate removal efficiency, and antifouling properties. Results showed significant improvements of the characteristics of modified... 

Condensation heat transfer on stainless steel tube utilizing superhydrophobic coatings was investigated. The electrophoretic deposition and spraying methods were employed to coat the tubes’ outer surface. The mixture that was synthesized for spray coating was a hybrid paint. It incorporated polyurethane matrix and a colloidal suspension containing organic nanoparticles. The hybrid paint had a proper adhesion to the substrate which caused more durability compared to the electrophoretic coating. The agglomeration of nanoparticles in the hybrid paint caused the formation of particles with larger size compared to the particles in the electrophoretic coating. Consequently, contact angle... 

Peripheral nerve injuries remain among the most challenging medical issues despite numerous efforts to devise methods in fabrication of nerve conduits to functionally regenerate axonal defects. In this regard, the current study offers a holistic perspective in design by considering the mechanical, topographical and structural aspects which are crucial for a successful nerve guide conduit. Poly(e-caprolactone) and gelatin were employed to serve this purpose in the form of dual-electrospun films which were rolled and later shaped the assembly of a multichannel conduit. Polyaniline/graphene (PAG) nanocomposite was incorporated to endow the conduit with conductive properties. FTIR analysis,... 

The wetting property of spherical particles in a hexagonal close-packed (HCP) ordering from extended Gibbs free energy (GFE) and Laplace pressure view points is studied. A formalism is proposed to predict the contact angle (θ) of a droplet on the HCP films and penetration angle (α) of the liquid on the spherical particles. Then, the extended Laplace pressure for the layered HCP ordering is calculated and a correlation between the wetting angle, sign of pressure, and pressure gradient is achieved. Our results show that the sign and the slope of pressure are important criteria for determining the wettability state and it is found that the contact angle is independent of the particle radius, as... 

A straightforward three-stage method was applied to fabricate a super-hydrophobic mixed-matrix nanofiber membrane using the electrospinning method for desalination purpose. First, a hydrothermal technique was applied to synthesize a super-hydrophobic nano-sheet, called octadecylamine-reduced graphene oxide (ODA-rGO) with a water contact angle of 162°, which was then added to PVDF-HFP dope solution. After, 0.005 wt% LiCl was added to the dope solution to decrease the mean pore size by increasing solution conductivity. Moreover, some membranes were hot-pressed to improve liquid entry pressure (LEP). Eventually, a top-quality nanofiber membrane was synthesized using 0.1 wt% ODA-rGO and 0.005... 

Condensation heat transfer on stainless steel tube utilizing superhydrophobic coatings was investigated. The electrophoretic deposition and spraying methods were employed to coat the tubes’ outer surface. The mixture that was synthesized for spray coating was a hybrid paint. It incorporated polyurethane matrix and a colloidal suspension containing organic nanoparticles. The hybrid paint had a proper adhesion to the substrate which caused more durability compared to the electrophoretic coating. The agglomeration of nanoparticles in the hybrid paint caused the formation of particles with larger size compared to the particles in the electrophoretic coating. Consequently, contact angle... 

Fog harvesting is an unconventional source of water that can be used in some regions with water scarcity to overcome water shortages. The most commonly used collectors are meshes which have intrinsic limitations, the most important of which are clogging and aerodynamic deviation of droplets around the wires. Here, three techniques are compared and combined to overcome these limitations, i.e., replacing the mesh with an array of vertical wires, addition of a hydrophobic layer to the wires, and forcing the ionized droplets to move toward the wires by applying an electric field. The combination of these techniques was found to result in higher fog harvesting efficiency compared to each... 

The authors have synthesized a superhydrophobic silica aerogel by using a sol-gel technique. The material is shown to be an efficient sorbent for needle trap microextraction of chlorobenzenes. Hydrophobicity affects the performance of the sorbent as shown by altering the ratio between tetraethylorthosilicate (TEOS) and methyltrimethoxysilane when synthesizing the sorbent. The observed contact angle (which is >150°) underpins the superhydrophobic properties of the aerogel. The microstructure of the sorbent was investigated by BET adsorption, revealing a surface area above 1000 m2 g−1. The sorbent was applied to needle trap extraction of chlorobenzenes from aqueous samples, and their... 

In this research, response surface methodology (RSM) was applied to study the effects of Na-Montmorillonite (Na-MMT) and glycerol on some functional properties of corn starch films. Films were prepared by casting method according to central composite design (CCD). Originally image processing technique was used in order to estimate transparency of the films. It was found that Na-MMT absorbed UV light from 216 to 266. nm. No antimicrobial activities were observed against Escherichia coli and Staphylococcus aureus. Contact angle analysis revealed hydrophilicity of starch films decreased utilizing nanoparticles and increased with plasticizer content. Increase in glycerol content decreased... 

Although several investigations have studied the low-salinity water injection (LSWI) performance during the past decades, the effect of crude oil type on the interfacial tension (IFT) and wettability alteration is still in dark. In this regard, this study is aimed to obtain the thermodynamic energies including adhesion, cohesion and spreading coefficient during LSWI. To achieve this goal, IFT and static contact angle values of three different crude oils (i.e. light, medium and heavy) are measured as a function of sea water salinity. The obtained results revealed that the dilution of sea water can change the wettability of reservoir rock from oil wet state towards water wet state, while crude...